GLEAM 1.0 - Assessment of greenhouse gas emissions and mitigation potential
Emissions from livestock supply chains
The livestock sector is a significant contributor to global human-induced GHG emissions. Livestock supply chains emitted an estimated total of 7.1 gigatonnes CO2-eq in 2005. This represents 14.5 percent of all human induced GHG emissions (IPCC, 2007). Methane (CH4) accounts for about 44 percent of the total. Nitrous oxide (N2O) and carbon dioxide (CO2) represent almost equal shares with 29 and 27 percent, respectively.
Global significance of sector's emissions. GHG emissions values are computed in GLEAM for 2005, while IPCC estimates are for 2004. GLEAM emissions estimate includes emissions attributed to edible products and to other goods and services.
Emissions by species
Cattle are the main contributor to the sector's emissions with about 4.6 gigatonnes CO2-eq, which represents about 65 percent of sector's emissions. Beef and dairy cattle generate similar amounts of greenhouse gases. Pigs, poultry, buffaloes and small ruminants have much lower emissions, representing between 7 and 10 percent of sector's emissions.
Global estimates of emissions by species. It includes emissions attributed to edible products and to other goods and services, such as draught power and wool. Beef cattle produce meat and non-edible outputs. Dairy cattle produce milk and meat as well as non-edible outputs.
Emissions by commodity and emission intensities
Beef meat and cattle milk are the two commodities with the highest total emissions, accounting for 2.9 and 1.4 gigatonnes CO2-eq, respectively. They are followed by pig meat, with 0.7 gigatonnes CO2-eq, buffalo meat and milk (0.6 gigatonnes CO2-eq), chicken meat and eggs (0.6 gigatonnes CO2-eq) and small ruminants meat and milk (0.4 gigatonnes CO2-eq). The rest of emissions are allocated to other poultry and non-edible products.
A way to compare the performance of different commodities is to express the emissions in terms on a per protein basis. By doing so, beef meat is the commodity with highest emission intensity, with an average of 342 kg CO2-eq per kg of protein. Meat and milk from small ruminants present the second and third highest emission intensities among commodities with averages of 165 and 112 kg CO2-eq per kg of protein. Cattle milk, chicken meat and eggs and pork have lower emission intensities, all below 100 kg CO2-eq per kg of protein. Emission intensities vary greatly among producers, especially in ruminant products. This reflects different agro-ecological conditions, farming practices and supply chains management. Is within this gap between high and low emission intensities where opportunities for mitigation can be found.
Global emission intensities by commodity. All commodities are expressed in a per protein basis. Averages are calculated at global scale and represent an aggregated value across different production systems and agro-ecological zones.
Emissions by source
Emissions from livestock supply chains originate from four main processes: enteric fermentation, manure management, feed production and energy consumption. GLEAM provides disaggregated information on emissions from those pathways.
Enteric fermentation accounts for the methane generated during the digestive process of ruminants -although non-ruminants species also produce methane when digesting, the amount is much lower. Feed quality is closely correlated with enteric emissions. Poorly digestible rations, i.e. highly fibrous ingredients, yield higher enteric methane emissions.
Manure acts as a source of both methane and nitrous oxide. Methane is released during anaerobic decomposition of organic matter. Nitrous oxide is mainly generated during manure ammonia decomposition. Different manure management systems (MMS) can lead to different emission levels. In general terms, methane emissions are higher when manure is stored and treated in liquid systems (lagoons or ponds), while dry MMS such as drylot or solid systems tend to favor nitrous oxide emissions.
There are several emissions related to feed production. Carbon dioxide emissions arise from expansion of feed crops and pastures into natural areas, from manufacture of fertilizers for feed crops and from feed transportation and processing. Nitrous oxide emissions are caused by the use of nitrogenous fertilizers and by direct application of manure both in pastures and crop fields.
Energy consumption occurs along the entire supply chain. Production of fertilizers and the use of machinery for crop management, harvesting, processing and transport of feed crops generate GHG emissions. Energy is also consumed on animal production site for ventilation, illumination, milking, cooling, etc. Finally, livestock commodities are processed, packed and transported to retail points, which involves further energy use.
Feed production accounts for almost 47 percent of total sector's emissions, with over 3.3 gigatonnes CO2-eq. Enteric fermentation is the second largest source of emissions, with 2.7 gigatonnes CO2-eq or about 40 percent of total emissions. Manure management is responsible for about 10 percent of the total, or 0.7 gigatonnes CO2-eq. Energy consumption, both on-farm and postfarm, account for 0.3 gigatonnes CO2-eq, or nearly 5 percent of the total.
Global emissions by source. Relative contribution of main sources of emissions from global livestock supply chains.
Livestock emissions by region
Regional emissions and production figures vary widely. Differences are explained by variations on the share of ruminant and monogastric species and emission intensities. GLEAM distinguishes different livestock production systems (LPS), namely grassland and mixed for ruminants; backyard, layers and broiler for chicken and backyard, intermediate and industrial for pigs. It allows a more accurate analysis of feed ration composition, MMS, energy consumption and the implications on GHG emissions.
Latin America and the Caribbean have the highest level of emissions, with 1.7 gigatonnes CO2-eq, caused by the specialized production of beef. Although it has dramatically reduced its pace in the last years, historical land-use changes contributed to high CO2 emissions arising from deforestation and pasture expansion. East and Southeast Asia, with over 1.0 gigatonnes CO2-eq, is the second highest emitting region. North America and Western Europe show similar levels of emissions (over 0.6 gigatonnes CO2-eq). South Asia presents a similar level of emissions as the latter region, but only about half of protein production level. Sub-Saharan Africa and Near East and North Africa present comparable emissions figures -slightly above 0.3 gigatonnes CO2-eq, while Eastern Europe, Oceania and Russian Federation share much lower emission levels (around 0.1 gigatonnes CO2-eq).
Regional emissions. Regional total emissions and their profile by animal species are shown. Results do not include emissions allocated to non-edible products and other services.
Livestock production by region
Production from livestock supply chains can be expressed as per protein basis, allowing comparisons between species and products. East and Southeast Asia, with about 14 million tonnes of protein, is the region with the highest production, mainly driven by monogastric species. Western Europe, North America and Latin America and the Caribbean have comparable production levels, between 9.5 and 9 million tonnes of protein. The profiles, however, are different: while beef and chicken play the main role in Latin and North America, Western Europe's production is primarily driven by the dairy cattle sector. South Asia is the fifth most important region in terms of production with just above 4 million tonnes of protein. Near East and north Africa, Sub-Saharan Africa, Eastern Europe, Oceania and Russian Federation, with production between 3 and 1.5 million tonnes of protein, have a lower individual share at global scale.
Regional production. Regional total production and their profile by commodity are shown. Meat production in protein basis was calculated by using data on dressing percentages, carcass to bone-free meat and average bone-free meat protein content. Milk from all species was converted into fat and protein corrected milk. Eggs production is also expressed in protein terms.
Emissions reduction from the livestock sector can be achieved by reducing production and consumption, by lowering emission intensity of production, or by a combination of the two. GLEAM does not evaluate the potential of reduced consumption of livestock products. Mitigation potential estimates in GLEAM are based on the wide gap in emission intensities that exists on a global and regional scale and within production systems and agro-ecological regions. The estimation for mitigation is around 30 percent, or about 1.8 gigatonnes CO2-eq, with respect to the baseline scenario. This figure arises from the assumption that producers in a given system, region and agro-ecological zone were to apply the practices of the 10th percentile of producers with the lowest emissions intensities, while maintaining constant output.
Mitigation potential of the global livestock sector. The mitigation potential estimate excludes changes between farming systems and assumes the overall output remains constant.